Derivative Financial Instruments (Tables)

6 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Summary of Outstanding Foreign Currency Forward Contracts

The following tables summarize our outstanding foreign currency forward contracts, by currency, at March 31, 2018 and September 30, 2017:

	March 31, 2018
	Contract Amount				Fair Value
	Foreign Currency		US$		US$
	(In thousands)
Sell foreign currency:
Euro (EUR)	EUR	5,250	$	6,506	$	—
Buy foreign currency:
British pound (GBP)	GBP	6,556	$	9,250	$	—
Singapore dollar (SGD)	SGD	8,363	$	6,400	$	—

	September 30, 2017
	Contract Amount				Fair Value
	Foreign Currency		US$		US$
	(In thousands)
Sell foreign currency:
Euro (EUR)	EUR	5,050	$	5,968	$	—
Buy foreign currency:
British pound (GBP)	GBP	9,341	$	12,500	$	—

Losses on Derivative Financial Instruments

Gains (losses) on derivative financial instruments are recorded in our condensed consolidated statements of income and comprehensive income as a component of other income (expense), net, and consisted of the following: 

	Quarter Ended March 31,				Six Months Ended March 31,
	2018		2017		2018		2017
	(In thousands)
Gains (losses) on foreign currency forward contracts	$	425	$	55	$	619	$	(505	)